View Compilation Error

0_0_18254526_24452.cpp: In function 'int main()':
0_0_18254526_24452.cpp:7:7: error: 'sum' was not declared in this scope
       sum += i;
       ^
0_0_18254526_24452.cpp:8:13: error: 'sum' was not declared in this scope
     cout << sum << endl << endl;
             ^